Am.  Jour  Phaem.  ) 
Nov.  1, 1871.  ; 
Compound  Iran  Mixture. 
505 
steel  point,  which  fits  into  a  small  hole  drilled  into  the  side  of  the 
pipe.  Bj  loosening  the  screw  more  or  less,  any  desirable  quantity 
of  air  can  be  here  constantly  admitted  and  a  pressure  obtained,  re- 
maining perfectly  uniform  during  the  operation. 
To  facilitate  the  filtration  of  larger  quantities  of 
^  liquids,  a  filtering  vessel,  (fig.  3)  has  been  constructed 
of  porcelain  or  metal,  in  which  the  disc  rests  upon  a 
sieve,  thus  presenting  a  large  surface  to  the  action  of 
the  vacuum.  The  funnel  end  of  this  vessel  prevents 
the  filtered  liquid  from  contact  with  the  rubber  gas- 
ket, and  permits  the  use  of  receiving-bottles  of  dif- 
ferent diameter  in  the  neck. 
Drying  of  Crystals  and  Herbs. — It  is  theoretically 
correct  that  water  boils  in  a  vacuum  of  720  mm.  at 
39*^  C,  and  it  might  be  supposed  that  damp  crystals 
and  fresh  herbs  could  be  rapidly  dried  therein.  The 
water,  however,  does  not  adhere  superficially  to  the 
plants,  but  is  contained  in  their  cells ;  they  therefore 
part  with  it  with  difficulty,  and  are  often  taken  out  of 
the  vacuum  in  an  almost  "scalded"  condition.  It  is  similar  with  crys- 
tals, which  do  not  lose  their  interstitial  water  any  quicker  in  vacuo 
than  in  the  open  air  :  and,  if  the  evaporation  is  facilitated  by  the 
application  of  heat,  the  water  of  crystallization  is  likely  to  be  like- 
wise expelled. 
For  many,  if  not  for  all  crystals  and  herbs,  not  the  rarification, 
but  a  current  of  air,  is  requisite  to  obtain  satisfactory  results,  and 
this  may  be  readily  produced  by  means  of  the  water  air-pump. 
In  conclusion,  the  authors  give  some  good  advice  about  the  put- 
ting up  and  the  use  of  this  instrument.  They  particularly  recom- 
mend to  employ  as  few  stop-cocks  as  possible,  which  soon  begin  to 
leak  under  greatly  reduced  pressure.  When,  after  some  experience, 
the  apparatus  has  received  its  most  advantageous  position,  some  of 
the  rubber  tubing  may  be  replaced  by  suitable  metallic  pipes. 
THE  COMPOUND  IRON  MIXTURE  OF  THE  PHARMACOPGEIA. 
By  0.  A,  Staples. 
This  has  always  been  a  favorite  medicine,  and,  when  carefully  pre- 
pared, is  perhaps  one  of  the  safest  and  most  efficacious  of  the  tonic 
